设计化合物8a-j以通过支架跳跃和改变烷氧基的长度来调节FTT的相互作用模式和亲油性。化合物8a,8d,8g,和BIBD-300通过酶抑制试验筛选高亲和力PARP-1,值得进一步评估。PARP-1中度表达的MCF-7皮下肿瘤的PET显像显示,与[18F]FTT相比,[18F]8a,[18F]8d,[18F]8g表现出更大的非特异性摄取,较低的目标与非目标比率,和严重的脱氟,而[18F]BIBD-300表现出较低的非特异性摄取和较高的靶与非靶比率。22Rv1皮下肿瘤的PET成像,高表达PARP-1,证实[18F]BIBD-300在正常器官中的摄取,比如肝脏,肌肉,还有骨头,低于[18F]FTT,肿瘤与肌肉和肿瘤与肝脏的比率[18F]BIBD-300大于[18F]FTT。小鼠MCF-7和22Rv1皮下肿瘤的生物分布结果进一步验证了PET成像的结果。与[18F]FTT不同,主要依靠肝胆清除,[18F]BIBD-300,具有较低的亲脂性,经历了从肝胆到肾清除的部分转变,提供[18F]BIBD-300指示肝癌的可能性。[18F]FTT的PET成像结果差异,[18F]BIBD-300,和[18F]8j在22Rv1小鼠和相应的分子对接结果进一步证实,亲脂性的细微结构修饰极大地优化了示踪剂的性质。细胞摄取实验还证明[18F]BIBD-300对PARP-1具有高亲和力。在大脑中检测到代谢和未代谢的[18F]FTT和[18F]BIBD-300,表明他们无法准确量化大脑中PARP-1的含量。然而,胶质瘤的PET成像显示,[18F]FTT和[18F]BIBD-300均可准确定位C6和U87MG肿瘤。基于其在乳腺癌诊断中的潜在优势,前列腺癌,还有神经胶质瘤,以及肝癌,[18F]BIBD-300是出色的PARP-1示踪剂的新选择。
Compounds 8a-j were designed to adjust the mode of interaction and lipophilicity of FTT by scaffold hopping and changing the length of the alkoxy groups. Compounds 8a, 8d, 8g, and BIBD-300 were screened for high-affinity PARP-1 through enzyme inhibition assays and are worthy of further evaluation. PET imaging of MCF-7 subcutaneous tumors with moderate expression of PARP-1 showed that compared to [18F]FTT, [18F]8a, [18F]8d, and [18F]8g exhibited greater nonspecific uptake, a lower target-to-nontarget ratio, and severe defluorination, while [18F]BIBD-300 exhibited lower nonspecific uptake and a greater target-to-nontarget ratio. PET imaging of 22Rv1 subcutaneous tumors, which highly express PARP-1, confirmed that the uptake of [18F]BIBD-300 in normal organs, such as the liver, muscle, and bone, was lower than that of [18F]FTT, and the ratio of tumor-to-muscle and tumor-to-liver [18F]BIBD-300 was greater than that of [18F]FTT. The biodistribution results in mice with MCF-7 and 22Rv1 subcutaneous tumors further validated the results of PET imaging. Unlike [18F]FTT, which mainly relies on hepatobiliary clearance, [18F]BIBD-300, which has lower lipophilicity, undergoes a partial shift from hepatobiliary to renal clearance, providing the possibility for [18F]BIBD-300 to indicate liver cancer. The difference in the PET imaging results for [18F]FTT, [18F]BIBD-300, and [18F]8j in 22Rv1 mice and the corresponding molecular docking results further confirmed that subtle structural modifications in lipophilicity greatly optimize the properties of the
tracer. Cell uptake experiments also demonstrated that [18F]BIBD-300 has a high affinity for PARP-1. Metabolized and unmetabolized [18F]FTT and [18F]BIBD-300 were detected in the brain, indicating that they could not accurately quantify the amount of PARP-1 in the brain. However, PET imaging of glioma showed that both [18F]FTT and [18F]BIBD-300 could accurately localize both in situ to C6 and U87MG tumors. Based on its potential advantages in the diagnosis of breast cancer, prostate cancer, and glioma, as well as liver cancer, [18F]BIBD-300 is a new option for an excellent PARP-1
tracer.